I've always liked the idea of an eclipse spell. It's just fun.

The other two make sense. If you use it, Radiant damage would work well. Another possibility would be blindness, 'cause, well, duh, or maybe confusion, since a lot of people think the moon causes madness.

As for other spells dealing with the moon, tidal effects could be cool. In the same way, concealment spells (like how the shadow of the earth covers the moon) might work. Some people also ascribe healing to the moon, so you could use that, too.